This happens usually when you transferring files between systems, for example, “scp” or “rsync” file from your local machine to a Linux server. The difference will show up when you have special characters (eg. ø, ó, ä … ) in your file, especially when your file is an HTML file, there will be garbled code showing up.
iconv -f iso-8859-1 -t utf-8 input.html > fixed_input.html
mv fixed_input.html input.html
Sometimes even if you have made sure that locally your file was encoded in utf-8, the transfer will still force recognize it as in iso-8859-1. This happens.